// Production steps of ECMA-262, Edition 6, 22.1.2.1
// es6-ified by @alexsasharegan
Iif (!Array.from) {
Array.from = (function() {
const toStr = Object.prototype.toString
const isCallable = fn => typeof fn === "function" || toStr.call(fn) === "[object Function]"
const toInteger = value => {
const number = Number(value)
if (isNaN(number)) {
return 0
}
if (number === 0 || !isFinite(number)) {
return number
}
return (number > 0 ? 1 : -1) * Math.floor(Math.abs(number))
}
const maxSafeInteger = Math.pow(2, 53) - 1
const toLength = value => Math.min(Math.max(toInteger(value), 0), maxSafeInteger)
// The length property of the from method is 1.
return function from(arrayLike /*, mapFn, thisArg */) {
// 1. Let C be the this value.
const C = this
// 2. Let items be ToObject(arrayLike).
const items = Object(arrayLike)
// 3. ReturnIfAbrupt(items).
if (arrayLike == null) {
throw new TypeError("Array.from requires an array-like object - not null or undefined")
}
// 4. If mapfn is undefined, then let mapping be false.
const mapFn = arguments.length > 1 ? arguments[1] : void undefined
let T
if (typeof mapFn !== "undefined") {
// 5. else
// 5. a If IsCallable(mapfn) is false, throw a TypeError exception.
if (!isCallable(mapFn)) {
throw new TypeError("Array.from: when provided, the second argument must be a function")
}
// 5. b. If thisArg was supplied, let T be thisArg; else let T be undefined.
if (arguments.length > 2) {
T = arguments[2]
}
}
// 10. Let lenValue be Get(items, "length").
// 11. Let len be ToLength(lenValue).
const len = toLength(items.length)
// 13. If IsConstructor(C) is true, then
// 13. a. Let A be the result of calling the [[Construct]] internal method
// of C with an argument list containing the single item len.
// 14. a. Else, Let A be ArrayCreate(len).
let A = isCallable(C) ? Object(new C(len)) : new Array(len)
// 16. Let k be 0.
let k = 0
// 17. Repeat, while k < len… (also steps a - h)
let kValue
while (k < len) {
kValue = items[k]
if (mapFn) {
A[k] = typeof T === "undefined" ? mapFn(kValue, k) : mapFn.call(T, kValue, k)
} else {
A[k] = kValue
}
k += 1
}
// 18. Let putStatus be Put(A, "length", len, true).
A.length = len
// 20. Return A.
return A
}
})()
}
Iif (!Array.isArray) {
Array.isArray = arg => Object.prototype.toString.call(arg) === "[object Array]"
}
// Static
export const from = Array.from
export const isArray = Array.isArray
// Instance
export const arrayIncludes = (array, value) => array.indexOf(value) !== -1
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